As one method of suppressing vibration of a robot arm, a vibration control method is known which includes: attaching an acceleration sensor to an arm tip; generating a compensation signal by using an acceleration signal to be generated by vibration and some robot parameters; and suppressing vibration by feeding back the compensation signal to be obtained to a torque command of each spindle motor (see, for example, JP-A-10-100085).
A block diagram of a vibration suppression controller utilizing a conventional vibration control method is illustrated in FIG. 1. A robot includes an arm 110 having a plurality of arm link units connected to each other via a joint unit, and an acceleration sensor 105 is arranged in the vicinity of the tip of the arm 110. A controller 108 which controls the movement of the arm 110 has a servo driver 114 which drives each joint unit of the arm 110 based on a velocity command value. An acceleration amount detected by the acceleration sensor 105 is input to a calculation unit 112. The calculation unit 112 calculates, based on the acceleration amount, a compensation component for each joint unit which compensates a velocity command value for each joint unit to the servo driver 114 so as to suppress vibration generated at the tip of the arm 110, and subtracts a value obtained by multiplying the calculated compensation component for each joint unit by a gain from the corresponding velocity command value.
When vibration control is performed, an acceleration sensor attached at the arm tip, an acceleration sensor interface which receives a signal from the acceleration sensor, and software for vibration control in which control for suppressing vibration is performed by feeding back a compensation signal to be obtained from a signal received via the acceleration sensor interface to a torque command of each spindle motor are required.
In a manufacturing line of a factory in which a plurality of robots are used, when a vibration control robot system is to be constructed, memory needs to be added to each robot controller; a board for the acceleration sensor interface is needed; and software for vibration control is required. However, it is difficult to incorporate these elements in existing robot controllers afterwards, resulting in cost increases.